a=int(input())
k=0
r=a//1000
r1=a//100
r2=a//10
r3=a
g=[]
k=0
if r%r==0 and r%1==0 and r%2!=0 and r%3!=0 and r%4!=0 and r%5!=0 and r%6!=0 and r%7!=0 and r%8!=0 and r%9!=0:
    g.append(r)
    k=k+1
else:
    print("0")
if r1%r1==0 and r1%1==0 and r1%2!=0 and r1%3!=0 and r1%4!=0 and r1%5!=0 and r1%6!=0 and r1%7!=0 and r1%8!=0 and r1%9!=0:
    g.append(r1)
    k=k+1
else:
    print("0")
if r2%r2==0 and r2%1==0 and r2%2!=0 and r2%3!=0 and r2%4!=0 and r2%5!=0 and r2%6!=0 and r2%7!=0 and r2%8!=0 and r2%9!=0:
    g.append(r2)
    k=k+1
else: 
    print("0")
if r3%r==0 and r3%1==0 and r3%2!= 0 and r3%3!=0 and r3%4!=0 and r3%5!=0 and r3%6!=0 and r3%7!=0 and r3%8!=0 and r3%9!=0:
    g.append(r3)
    k=k+1
else:
    print("0")
if k>0:
    print(max(g))
else:
    print("0")
